1. Field of the Invention
An aspect of this disclosure relates to an optical sensor and an image forming apparatus. Specifically, the aspect of this disclosure relates to an optical sensor including a semiconductor laser and an image forming apparatus including the optical sensor.
2. Description of the Related Art
An image forming apparatus, such as a digital copier or a laser printer, transfers a toner image onto a surface of a recording medium, such as a printing paper. Then the image forming apparatus fixes the toner image by heating and pressing the toner image under a predetermined condition, thereby forming an image.
A fixing property of the toner image is affected to a large degree by a material, a thickness, a degree of humidity, a degree of smoothness, and a coating condition of the recording medium. For example, for a recording medium whose degree of smoothness is low and whose surface has significant irregularities, a fixing ratio at a concave portion is low, and it is possible that an unevenness in color occurs. Therefore, in order to perform a high quality image formation, it may be required to set a fixing condition individually depending on the type of recording medium.
Further, in accordance with the advancement in the image forming apparatus and the diversification in the methods of expression, there are more than several hundred types of recording media only for the printing papers. Furthermore, for each type of the printing paper, there is a wide variety of names depending on the difference in the basis weight or in the thickness.
Types of mainly used printing papers include a regular paper; a coated paper, such as a gloss coated paper, a matt coated paper, and an art paper; a plastic sheet paper; and a specialty paper whose surface is embossed. The names of the above papers are also increasing.
In a present image forming apparatus, a user may be required to set the fixing condition at a time of printing. Therefore, the user may be required to have knowledge for identifying the type of paper. Furthermore, there is a bother such that, each time, the user may be required to enter a content of a setting corresponding to the type of the paper. When an erroneous content of the setting is entered, an optimized image is not obtained.
Incidentally, Patent Document 1 (Japanese Published Unexamined Publication No. 2002-340518) discloses a surface property identifying device that includes a sensor that identifies a surface property of a recording material by scanning the surface of the recording material while contacting the surface of the recording material.
Patent Document 2 (Japanese Published Unexamined Publication No. 2003-292170) discloses a printing device that determines a type of printing paper based on a pressure value, the pressure value being detected with a pressure sensor when the pressure sensor contacts the printing paper.
Patent Document 3 (Japanese Published Unexamined Publication No. 2005-156380) discloses a recording material determining device which determines a type of recording material using reflected light and transmitted light.
Patent Document 4 (Japanese Published Unexamined Publication No. HEI10-160687) discloses a sheet material determining device which determines a material of a sheet under conveyance based on an amount of light reflected on a surface of the sheet material and an amount of light transmitted through the sheet material.
Patent Document 5 (Japanese Published Unexamined Publication No. 2006-062842) discloses an image forming apparatus including determining means for determining whether a recording material is stored in a feeding unit and whether the feeding unit exists, based on a detection output from a reflection-type optical sensor.
Patent Document 6 (Japanese Published Unexamined Publication No. HEI11-249353) discloses an image forming apparatus that determines a surface property of a recording medium by irradiating light to the recording medium and detecting respective amounts of two polarization components of the reflected light.
The recording material determining device disclosed in Patent Document 3, however, can determine only a degree of smoothness of a surface of a printing paper. The recording material determining device does not distinguish between names of printing papers, the names of recording papers having the same degree of smoothness but having different thicknesses. Further, depending on an imaging device that is used in the recording material determining device, a blur occurs on a read image and a high quality image is not obtained. Thus it is difficult to identify the recording material accurately. In order to reduce the blur, a higher performance device may be required, but it is disadvantageous since it leads to a higher cost. Further, even if the high quality image is obtained, there is another disadvantage that a high performance image analyzing device may be required to identify the recording material from the high quality image.
Further, with the sheet material determining device disclosed in Patent Document 4 and with the image forming apparatuses disclosed in Patent Document 5 and Patent Document 6, only differences among non-coated paper/coated paper/OHP sheet can be identified (determined). The sheet material determining device disclosed in Patent Document 4 and the image forming apparatuses disclosed in Patent Document 5 and Patent Document 6 do not distinguish among the names. It may be required to distinguish among the names to form a high quality image.